In the equatorial reference frame, the reference plane is the plane of the Earth's equator, and the reference direction is the direction of the vernal equinox. the plane of the Earth's orbit around th...In the equatorial reference frame, the reference plane is the plane of the Earth's equator, and the reference direction is the direction of the vernal equinox. the plane of the Earth's orbit around the Sun), and the reference direction is again in the direction of the vernal equinox. The plane of the equator and the plane of the ecliptic intersect along a line, and the direction of the vernal equinox lies along that line of intersection.
